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排序方式: 共有169条查询结果,搜索用时 15 毫秒
51.
粒子加速器由于受地基振动、环境温度、热效应等因素的影响,导致束流位置探头(BPM)所在真空盒的机械中心相对四极铁磁中心的漂移较大,因此很难提高束流轨道的绝对测量精度。探索利用电容式探头实时检测该漂移量的方法。首先分析了电容式探头的测量原理,并设计了轨道振动同步诊断方案,然后设计了专用探头,并利用数据采集设备对探头的线性度、精度和频率响应进行实验室测试。结果显示电容式探头能检测到2μm的相对位移,且可有效检测300Hz以下的振动频率,可用于束流轨道与相关环境参数的同步诊断。 相似文献
52.
In this paper, a multigrid method based on the high order compact (HOC) difference scheme on nonuniform grids, which has been proposed by Kalita et al. [J.C. Kalita, A.K. Dass, D.C. Dalal, A transformation-free HOC scheme for steady convection–diffusion on non-uniform grids, Int. J. Numer. Methods Fluids 44 (2004) 33–53], is proposed to solve the two-dimensional (2D) convection diffusion equation. The HOC scheme is not involved in any grid transformation to map the nonuniform grids to uniform grids, consequently, the multigrid method is brand-new for solving the discrete system arising from the difference equation on nonuniform grids. The corresponding multigrid projection and interpolation operators are constructed by the area ratio. Some boundary layer and local singularity problems are used to demonstrate the superiority of the present method. Numerical results show that the multigrid method with the HOC scheme on nonuniform grids almost gets as equally efficient convergence rate as on uniform grids and the computed solution on nonuniform grids retains fourth order accuracy while on uniform grids just gets very poor solution for very steep boundary layer or high local singularity problems. The present method is also applied to solve the 2D incompressible Navier–Stokes equations using the stream function–vorticity formulation and the numerical solutions of the lid-driven cavity flow problem are obtained and compared with solutions available in the literature. 相似文献
53.
Science China Chemistry - Multicolor fluorescent probes based on small organic molecules have the advantages of low cost, good biocompatibility, easily modifiable molecular structures and... 相似文献
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机器学习技术在近十几年发展迅猛,并被广泛地用于解决复杂的科学和工程问题。最近十年间,基于机器学习的粒子加速器相关研究也开始呈现出井喷式发展趋势。国际上许多加速器实验室开始尝试用机器学习和大数据技术处理加速器中的海量复杂数据,以期解决加速器及其子系统中的诸多物理和技术问题。不过,迄今为止,机器学习在加速器中的应用仍处于初步探索阶段,不同机器学习算法在解决具体加速器问题的效果及其适用范围尚待摸索,机器学习在实际加速器中的应用仍非常有限。因此,有必要对加速器领域中的机器学习研究做一个整体回顾和总结。将回顾机器学习在大型粒子加速器(以储存环加速器和直线加速器为主)中的加速器技术、束流物理以及加速器整体性能优化等研究方向中已取得的研究成果,并探讨机器学习在加速器领域的未来发展方向和应用前景。
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分析了统计最优近场声全息(Statistically optimized nearfield acousticholography,简称SONAH)的重建过程发现采用SONAH重建噪声源表面法向振速时误差较大的原因在于正则化参数选取较小。在此基础上提出一种单元平面波优化选择方法,该方法保留了单元平面波中的全部传播波和部分倏逝波,去除了一些较高波数的倏逝波成分,保证了重建过程中正则化参数的准确选取。另外,采用单元平面波优化选择方法还可以降低SONAH中传递矩阵的阶数,从而解决SONAH的计算速度随着测量点数目的增加急剧变慢的问题。通过数值仿真和实验对所提出的单元平面波优化选择方法的有效性进行了验证,结果表明采用该方法后SONAH的计算速度和法向振速的重建精度都得到了较大提高。 相似文献
59.
Feng Y Lin J Lin Z Li H 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2006,63(2):266-271
Cis-N-[4-[4-(1,2-benzisozole-3-yl)-1-piperazinyl]butyl]cyclohexane-1,2-dicarboximide monohydrochloride dihydrate was studied spectroscopically. Complete NMR assignments were made using DEPT, H-H COSY, as well as HMQC and HMBC heteronuclear correlation techniques. The hydrochloride salt was found at delta > 10. The dihydrate was present in the region delta 3-4 in DMSO-d6 solvent. Asymmetry carbon C3 brought chemical-shift-nonequivalent of cis-cyclohexanyl group, splitting four systems H1, H1', H2 and H2'. Diamagnetic anisotropy of benzisozolyl group results in three troops peaks of piperazinyl group. 相似文献
60.
Nitrogen,Phosphorus, and Sulfur Co‐Doped Hollow Carbon Shell as Superior Metal‐Free Catalyst for Selective Oxidation of Aromatic Alkanes 下载免费PDF全文
Shuliang Yang Dr. Li Peng Peipei Huang Xiaoshi Wang Yongbin Sun Dr. Changyan Cao Prof. Weiguo Song 《Angewandte Chemie (International ed. in English)》2016,55(12):4016-4020
Metal‐free heteroatom‐doped carbocatalysts with a high surface area are desirable for catalytic reactions. In this study, we found an efficient strategy to prepare nitrogen, phosphorus, and sulfur co‐doped hollow carbon shells (denote as NPS‐HCS) with a surface area of 1020 m2 g?1. Using a poly(cyclotriphosphazene‐co‐4,4′‐sulfonyldiphenol) (PZS) shell as carbon source and N, P, S‐doping source, and the ZIF‐67 core as structural template as well as extra N‐doping source, NPS‐HCS were obtained with a high surface area and superhydrophilicity. All these features render the prepared NPS‐HCS a superior metal‐free carbocatalyst for the selective oxidation of aromatic alkanes in aqueous solution. This study provides a reliable and facile route to prepare doped carbocatalysts with enhanced catalytic properties. 相似文献